Norman Cohn

Norman Cohn

The distinguished historian Norman Cohn, who has died aged 92, unearthed the roots of European barbarism. His best known study, The Pursuit of the Millennium: Revolutionary Millenarians and Mystical Anarchists of the Middle Ages (1957), demonstrated convincingly that the totalitarian ideologies of the 20th century, chiefly Marxism and nazism, shared a "common stock of European social mythology" with apocalyptic medieval movements such as the Flagellants and the Anabaptists.

Common to both modern and medieval versions of this ideology was a belief in the end of history, culminating, after much suffering and struggle, in an earthly paradise for an elect, and the destruction of their enemies. Just as the established church, rich landowners and Jews were to be swept away by the poor of medieval Europe, so the "world Jewish conspiracy" was to make way for the Third Reich, or the Marxist proletariat succeed the bourgeoisie. This enduring strain of belief has found more recent echoes in both Islamism and the US evangelical right.

Cohn was born in London to a Jewish father and Roman Catholic mother. He gained a scholarship to Gresham's school in Holt, Norfolk, where he demonstrated talent as a linguist. In 1936, he took a first in medieval and modern languages at Christ Church, Oxford, where he undertook research until the outbreak of the second world war, when he enrolled in the Queen's Royal Regiment. His interest in totalitarian ideologies and their roots in medieval Europe can be traced back to his experiences in postwar Vienna when, as an officer in the Intelligence Corps, he interrogated members of the SS and met refugees fleeing the horrors of Soviet-dominated eastern Europe.

Returning to academia on demobilisation, as a lecturer in French at Glasgow University (1946-51), he embarked on the studies that would make his reputation, despite having no formal training as an historian. Indeed, his very unorthodoxy may account for the originality of his insights. His mastery of medieval Latin, Greek, Old French and High and Low German was to prove invaluable as he spent a decade combing European archives for the primary sources that resulted in The Pursuit of the Millennium. Written with style and great clarity, it revealed a remarkable array of revolutionary, heretical medieval movements, strongly influenced by the Bible's book of Revelation, who were opposed to the orthodox Augustinian view that the Roman Catholic church had fully realised the millennium (a state of spiritual perfection) on Earth.

Within this apocalyptic tradition, Cohn identified the Flagellants who massacred the Jews of Frankfurt in 1349; the widespread heresy of the Free Spirit; the 16th-century Anabaptist theocracy of Münster (though some have criticised Cohn's account of this extraordinary event as lurid); the Bohemian Hussites; the instigators of the German peasants' war; and the Ranters of the English civil war. In one of the work's most striking insights, Cohn claimed that Joachim of Fiore, a 12th-century Calabrian abbot, anticipated Marxism, with Joachim's successive ages of the Father, the Son and the Spirit reappearing as primitive communism, class society and the final withering away of the state.

The success of the book, which was revised with regularity by Cohn and translated into a dozen languages, opened up new professional challenges. In 1951, he was appointed professor of French at Magee University College, Derry, and took a similar post at Newcastle University in 1960. But in 1963 he became a professional historian, accepting directorship of the Columbus centre for studies of persecution and genocide at the University of Sussex.

There, he researched and wrote Warrant for Genocide (1967), a study of The Protocols of the Elders of Zion, the forged document from the turn of the century that had purported to reveal a global Jewish conspiracy and eventually played a key role in Nazi mythology. Cohn revealed how the anti-semitism of the medieval European mind remained very much alive in the 20th century and was resurgent in times of rapid social change and dislocation.

In 1973, Cohn became Astor-Wolfson professor of history at Sussex. He had turned his attention to another fantasy, that which inspired the great European witch-hunt of the 16th and 17th centuries, resulting in Europe's Inner Demons: An Enquiry Inspired by the Great Witch-hunt (1976). Cohn argued that the fantasy of the witch belonged to a longstanding tradition that imagined a small, secret society opposed to, but within, the greater society that it sought to destroy. He found precursors of the witch-hunts in the persecution of early Christians by the Romans, in the Church's campaigns against 12th-century heretics, and in the destruction of the Knights Templars.

Cohn became professor emeritus at Sussex in 1980, though advised Concordia University, Montreal, on the comparative study of genocide (1982-85), and thereafter was involved with the Montreal Institute for Genocide Studies. He was also a visiting professor at King's College London (1986-89) and wrote two further works. In the first, Cosmos, Chaos and the World to Come: The Ancient Roots of Apocalyptic Faith (1993), Cohn studied the ancient civilisations of Egypt, Mesopotamia and Vedic India in order to trace the source of millennial speculation, which he claimed to find in Zoroastrianism. In his last book, Noah's Flood: The Genesis Story in Western Thought (1999), he explored the origins, development and varying interpretations of the ancient story of Noah.

As Cohn himself pointed out, all his work was fundamentally concerned with the study of the same phenomenon: "the urge to purify the world through the annihilation of some category of human beings imagined as agents of corruption and incarnations of evil". His experience of war, his encounters with the totalitarian regimes of the 20th century and the suffering of his German relatives in the Holocaust informed his writings, giving them an urgency and energy lacking in many other historical surveys.

But as well as being brilliant works of history, they are also warnings, that the subterranean fantasies that have scarred European history are with us still. "There are times," Cohn wrote, "when this underworld emerges from the depths and suddenly fascinates, captures and dominates multitudes of usually sane and responsible people who thereupon take leave of sanity and responsibility. And it occasionally happens that this underworld becomes a political power and changes the course of history."

A fellow of both the Royal Historical Society and the British Academy, and recipient of widespread international recognition, Cohn was a modest man who never sought publicity. He is survived by his second wife, Marina Voikhanskaya, whom he married in 2004, and his son, Nik Cohn, whose distinguished writings on popular music reveal a similarly unorthodox and insightful mind. His first wife, Vera Broido, whom he married in 1941, died in 2004.

· Norman Rufus Colin Cohn, historian and linguist, born January 12 1915; died July 31 2007

Richard Webster writes:

It was Anthony Storr who best summed up the work of one of the greatest modern scholars when he wrote that "Norman Cohn is the historian of important parts of history other historians do not reach." The key to his extraordinary achievement perhaps lay in the fact that in his own life the personal and political were never severed, and matters of the heart were as important to him as matters of the head. In 1941 he embraced a tradition of dissidence when he married the historian Vera Broido, the daughter of Menshevik revolutionaries, who had previously lived in a ménage à trois with Raoul Hausmann, one of the founders of Dada.

After Vera's death at the age of 96, Norman was too open to life and to new possibilities to remain a widower for long. Lucid and intellectually alert almost to the end, he became close to another political exile, the psychiatrist Marina Voikhanskaya, who had left the Soviet Union after refusing to declare one of her patients - a dissident - insane. When I last met him in December 2004, he was genial, hospitable, radiant with his recent marriage to her and looking forward to a late honeymoon in Provence during which he would celebrate his 90th birthday.

His greatness will always reside in the manner he combined deep scholarship with a passionate zest for life. It was this which informed his critique of ideologies of purity and his recognition of the dangers that they posed. And it was this which made him, as Isaiah Berlin acknowledged when he recommended him for election as a fellow of the British Academy, one of the greatest of all modern historians.